1.
Serial communication
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In telecommunication and data transmission, serial communication is the process of sending data one bit at a time, sequentially, over a communication channel or computer bus. This is in contrast to parallel communication, where bits are sent as a whole. Serial communication is used for all communication and most computer networks. The migration from PCI to PCI Express is an example, many serial communication systems were originally designed to transfer data over relatively large distances through some sort of data cable. Practically all long-distance communication transmits data one bit at a time, rather than in parallel, the cables that carry this data and the computer ports they plug into are usually referred to with a more specific name, to reduce confusion. Keyboard and mouse cables and ports are almost invariably serial—such as PS/2 port and Apple Desktop Bus, many communication systems were generally originally designed to connect two integrated circuits on the same printed circuit board, connected by signal traces on that board. Integrated circuits are more expensive when they have more pins, to reduce the number of pins in a package, many ICs use a serial bus to transfer data when speed is not important. Some examples of such low-cost serial buses include SPI, I²C, dc-bus, UNI/O, the communication links across which computers—or parts of computers—talk to one another may be either serial or parallel. A parallel link transmits several streams of data simultaneously along multiple channels, whereas, several factors allow serial to be clocked at a higher rate, Clock skew between different channels is not an issue. A serial connection requires fewer interconnecting cables and hence occupies less space, the extra space allows for better isolation of the channel from its surroundings. Crosstalk is less of an issue, because there are fewer conductors in proximity, in many cases, serial is cheaper to implement than parallel. Many ICs have serial interfaces, as opposed to parallel ones, so that they have fewer pins and are therefore less expensive
2.
BNC connector
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The BNC connector is a miniature quick connect/disconnect radio frequency connector used for coaxial cable. It features two bayonet lugs on the connector, mating is fully achieved with a quarter turn of the coupling nut. BNC connectors are used with coaxial cable in radio, television, and other radio-frequency electronic equipment, test instruments. The BNC was commonly used for computer networks, including ARCnet, the IBM PC Network. BNC connectors are made to match the impedance of cable at either 50 ohms or 75 ohms. They are usually applied for frequencies below 4 GHz and voltages below 500 volts, similar connectors using the bayonet connection principle exist, and a threaded connector is also available. The BNC was originally designed for use and has gained wide acceptance in video. The BNC uses a slotted outer conductor and some plastic dielectric on each gender connector and this dielectric causes increasing losses at higher frequencies. Above 4 GHz, the slots may radiate signals, so the connector is usable, both 50 ohm and 75 ohm versions are available. The BNC connector is used for signal connections such as, analog, the BNC connector is used for composite video on commercial video devices. Consumer electronics devices with RCA connector jacks can be used with BNC-only commercial video equipment by inserting an adapter, BNC connectors were commonly used on 10base2 thin Ethernet network cables and network cards. BNC connections can also be found in recording studios, digital recording equipment uses the connection for synchronization of various components via the transmission of word clock timing signals. Typically the male connector is fitted to a cable, and the female to a panel on equipment, cable connectors are often designed to be fitted by crimping using a special power or manual tool. Wire strippers which strip outer jacket, shield braid, and inner dielectric to the lengths in one operation are used. The connector was named the BNC after its bayonet mount locking mechanism and its inventors, Paul Neill, Neill worked at Bell Labs and also invented the N connector, Concelman worked at Amphenol and also invented the C connector. A backronym has been applied to it, British Naval Connector. Another common incorrectly attributed origin is Berkeley Nucleonics Corporation, the basis for the development of the BNC connector was largely the work of Octavio M. Salati, a graduate of the Moore School of Electrical Engineering of the University of Pennsylvania. In 1945, while working at Hazeltine Electronics Corporation, he filed a patent for a connector for coaxial cables that would minimize wave reflection/loss, the patent was granted in 1951
3.
Society of Motion Picture and Television Engineers
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SMPTE Membership is open to any individual or organization with interest in the subject matter. SMPTE standards documents are copyrighted and may be purchased from the SMPTE website, standard documents may be purchased by the general public. Significant standards promulgated by SMPTE include, All film and television formats and media. The society sponsors many awards, the oldest of which are the SMPTE Progress Medal, the Samuel Warner Memorial Medal, SMPTE also has a number of student Chapters and sponsors scholarships for college students in the motion imaging disciplines. A group within the standards committees has begun to work on the definition of the SMPTE 3D Home Master. SMPTE, instituted in 1999, a committee for the foundations of Digital Cinema. The SMPTE presents awards to individuals for outstanding contributions in fields of the society, James Cameron Edwin Catmull Birney Dayton Clyde D. Smith Roderick Snell Dr. Kees Immink Stanley N. Baron William C. Miller Bernard J. Lechner Ray Dolby Harold E. Edgerton Vladimir K. Zworykin John G. Frayne Walt Disney Chuck Pagano James M. DeFilippis Bernard J. Lechner Stanley N. Baron William F. Schreiber Adrian Ettlinger Joseph A. Flaherty, goldmark W. R. G. Baker Albert Rose Charles Ginsburg Robert E. Shelby Arthur V. Loughren Otto H. Recent recipients are Andrew Laszlo James MacKay Dr. Roderick T. Swartz
4.
Broadcasting
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Broadcasting began with AM radio, which came into popular use around 1920 with the spread of vacuum tube radio transmitters and receivers. Before this, all forms of communication were one-to-one, with the message intended for a single recipient. Over the air broadcasting is usually associated with radio and television, the receiving parties may include the general public or a relatively small subset, the point is that anyone with the appropriate receiving technology and equipment can receive the signal. The field of broadcasting includes both government-managed services such as radio, community radio and public television, and private commercial radio. The U. S. Code of Federal Regulations, title 47, part 97 defines broadcasting as transmissions intended for reception by the general public, private or two-way telecommunications transmissions do not qualify under this definition. For example, amateur and citizens band radio operators are not allowed to broadcast, as defined, transmitting and broadcasting are not the same. Transmissions using a wire or cable, like television, are also considered broadcasts. In the 2000s, transmissions of television and radio programs via streaming digital technology have increasingly been referred to as broadcasting as well, the earliest broadcasting consisted of sending telegraph signals over the airwaves, using Morse code, a system developed in the 1830s by Samuel F. B. Morse, physicist Joseph Henry and Alfred Vail and they developed an electrical telegraph system which sent pulses of electric current along wires which controlled an electromagnet that was located at the receiving end of the telegraph system. A code was needed to transmit natural language using only these pulses, Morse therefore developed the forerunner to modern International Morse code. Audio broadcasting began experimentally in the first decade of the 20th century, by the early 1920s radio broadcasting became a household medium, at first on the AM band and later on FM. Television broadcasting started experimentally in the 1920s and became widespread after World War II, satellite broadcasting was initiated in the 1960s and moved into general industry usage in the 1970s, with DBS emerging in the 1980s. Originally all broadcasting was composed of signals using analog transmission techniques but in the 2000s. In general usage, broadcasting most frequently refers to the transmission of information, Analog audio vs. HD Radio Analog television vs.9 zettabytes. This is the equivalent of 55 newspapers per person per day in 1986. Historically, there have been several methods used for broadcasting electronic media audio and/or video to the public, Telephone broadcasting. Telephone broadcasting also grew to include telephone services for news and entertainment programming which were introduced in the 1890s. These telephone-based subscription services were the first examples of electrical/electronic broadcasting, Radio broadcasting, audio signals sent through the air as radio waves from a transmitter, picked up by an antenna and sent to a receiver
5.
Digital cinema
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Digital cinema refers to the use of digital technology to distribute or project motion pictures as opposed to the historical use of reels of motion picture film, such as 35 mm film. Digital movies are projected using a digital projector instead of a film projector. Digital cinema is distinct from high-definition television and is not dependent on using television or high-definition video standards, aspect ratios, in digital cinema, resolutions are represented by the horizontal pixel count, usually 2K or 4K. As digital cinema technology improved in the early 2010s, most of the theaters across the world converted to digital, Digital media playback of high-resolution 2K files has at least a 20-year history. Early video data storage units fed custom frame buffer systems with large memories, in early digital video units, content was usually restricted to several minutes of material. Transfer of content between remote locations was slow and had limited capacity and it was not until the late 1990s that feature-length films could be sent over the wire. In conjunction with Texas Instruments, the movie was publicly demonstrated in five theaters across the United States. In Europe, on February 2,2000, Texas Instruments DLP Cinema projector technology was demonstrated, by Philippe Binant. On January 19,2000, the Society of Motion Picture and Television Engineers, in the United States, by December 2000, there were 15 digital cinema screens in the United States and Canada,11 in Western Europe,4 in Asia, and 1 in South America. Digital Cinema Initiatives was formed in March 2002 as a joint project of many motion picture studios to develop a specification for digital cinema. In April 2004, in cooperation with the American Society of Cinematographers, DCI created standard evaluation material for testing of 2K and 4K playback, DCI selected JPEG2000 as the basis for the compression in the system the same year. In China, in June 2005, an E-Cinema System called dMs was established and was used in over 15,000 screens spread across Chinas 30 provinces, DMS estimated that the system would expand to 40,000 screens in 2009. In 2005 the UK Film Council Digital Screen Network launched in the UK by Arts Alliance Media creating a chain of 250 2K digital cinema systems, the roll out was completed in 2006. This was the first mass roll out in Europe, axis IT/Christie Digital also started a roll out in the United States and Canada. By mid 2006, about 400 theaters were equipped with 2K digital projectors with the number increasing every month, several digital 3D films surfaced in 2006 and several prominent filmmakers committed to making their next productions in stereo 3D. VUE West End was one of the first 3D Digital Cinemas along with Odeon Printworks Manchester and this was done by Emil and Eric Digital Films, a company based at Thrissur using the end-to-end digital cinema system developed by Singapore-based DG2L Technologies. This film was mastered at Real Image Media Technologies in India. In June 2007, Arts Alliance Media announced the first European commercial digital cinema Virtual Print Fee agreements, by June 2010, there were close to 16,000 digital cinema screens, with over 5000 of them being stereoscopic setups
6.
Digital single-lens reflex camera
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A digital single-lens reflex camera is a digital camera that combines the optics and the mechanisms of a single-lens reflex camera with a digital imaging sensor, as opposed to photographic film. The reflex design scheme is the difference between a DSLR and other digital cameras. In the reflex design, light travels through the lens, then to a mirror that alternates to send the image to either the viewfinder or the image sensor, the alternative would be to have a viewfinder with its own lens, hence the term single lens for this design. By using only one lens, the viewfinder of a DSLR presents an image that will not perceptibly differ from what is captured by the cameras sensor, like SLRs DSLRs typically use interchangeable lenses with a proprietary lens mount. A movable mechanical mirror system is switched down to light from the lens over a matte focusing screen via a condenser lens. Most of the entry-level DSLRs use a instead of the traditional pentaprism. Focusing can be manual or automatic, activated by pressing half-way on the release or a dedicated AF button. DSLRs typically use autofocus based on phase detection and this method allows the optimal lens position to be calculated, rather than found, as would be the case with autofocus based on contrast maximisation. Phase-detection autofocus is typically faster than other passive techniques, as the phase sensor requires the same light going to the image sensor, it was previously only possible with an SLR design. Digital SLR cameras, along with most other cameras, generally have a mode dial to access standard camera settings or automatic scene-mode settings. Sometimes called a PASM dial, they typically provide such as program, aperture-priority, shutter-priority. Scene modes vary from camera to camera, and these modes are inherently less customizable and they often include landscape, portrait, action, macro, night, and silhouette, among others. However, these different settings and shooting styles that scene mode provides can be achieved by calibrating certain settings on the camera, professional DSLRs seldom contain automatic scene modes as professionals often do not require these and professionals know how to achieve the looks they want. A method to prevent dust entering the chamber, by using a dust cover filter right behind the mount, was used by Sigma in its first DSLR. Olympus used a built-in sensor cleaning mechanism in its first DSLR that had a sensor exposed to air, several Canon DSLR cameras rely on dust reduction systems based on vibrating the sensor at ultrasonic frequencies to remove dust from the sensor. Interchangeable lenses for SLRs and DSLRs are built to operate correctly with a lens mount that is generally unique to each brand. There are also lens adapters that allow a lens for one mount to be used on a camera body with a different lens mount. Many lenses are mountable, diaphragm-and-meter-compatible, on modern DSLRs and on older film SLRs that use the lens mount
7.
HDMI
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HDMI is a digital replacement for analog video standards. HDMI implements the EIA/CEA-861 standards, which video formats and waveforms, transport of compressed, uncompressed, and LPCM audio, auxiliary data. CEA-861 signals carried by HDMI are electrically compatible with the CEA-861 signals used by the visual interface. No signal conversion is necessary, nor is there a loss of quality when a DVI-to-HDMI adapter is used. The CEC capability allows HDMI devices to each other when necessary. Several versions of HDMI have been developed and deployed since initial release of the technology but all use the same cable and connector. Other than improved audio and video capacity, performance, resolution and color spaces, newer versions have optional advanced features such as 3D, Ethernet data connection, production of consumer HDMI products started in late 2003. In Europe either DVI-HDCP or HDMI is included in the HD ready in-store labeling specification for TV sets for HDTV, HDMI began to appear on consumer HDTV camcorders and digital still cameras in 2006. As of January 6,2015, over 4 billion HDMI devices have been sold, the HDMI founders are Hitachi, Panasonic, Philips, Silicon Image, Sony, Thomson, RCA and Toshiba. Digital Content Protection, LLC provides HDCP for HDMI, HDMI has the support of motion picture producers Fox, Universal, Warner Bros. and Disney, along with system operators DirecTV, EchoStar and CableLabs. The HDMI founders began development on HDMI1.0 on April 16,2002, at the time, DVI-HDCP and DVI-HDTV were being used on HDTVs. HDMI1.0 was designed to improve on DVI-HDTV by using a connector and adding audio capability and enhanced YCbCr capability. The first Authorized Testing Center, which tests HDMI products, was opened by Silicon Image on June 23,2003, in California, the first ATC in Japan was opened by Panasonic on May 1,2004, in Osaka. The first ATC in Europe was opened by Philips on May 25,2005, in Caen, the first ATC in China was opened by Silicon Image on November 21,2005, in Shenzhen. The first ATC in India was opened by Philips on June 12,2008, the HDMI website contains a list of all the ATCs. According to In-Stat, the number of HDMI devices sold was 5 million in 2004,17.4 million in 2005,63 million in 2006, and 143 million in 2007. HDMI has become the de facto standard for HDTVs, and according to In-Stat, In-Stat has estimated that 229 million HDMI devices were sold in 2008. On April 8,2008 there were over 850 consumer electronics, on January 7,2009, HDMI Licensing, LLC announced that HDMI had reached an installed base of over 600 million HDMI devices
8.
Modchip
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A modchip is a small electronic device used to alter or disable artificial restrictions of computers or entertainment devices. Modchips are mainly used in videogame consoles, but also in some DVD or Blu-ray players, modchips operate by replacing or overriding a systems protection hardware or software. Most modchips consist of one or more integrated circuits, often complemented with discrete parts, although there are modchips that can be reprogrammed for different purposes, most modchips are designed to work within only one console system or even only one specific hardware version. Memory cards or cartridges that offer functions similar to work on a completely different concept. Such devices are not referred to as modchips, even if they are traded under this umbrella term. Some of the first modchips for the Nintendo Wii known as chips, modify the behaviour. While on the Xbox 360, a common modchip took advantage of the short periods of instability in the CPU could be used to fairly reliably lead it to incorrectly compare security signatures. The precision required in this meant the modchip made use of a CPLD. Other modchips, such as the XenoGC and clones for the Nintendo GameCube, invoke a debug mode where security measures are reduced or absent, in this case a stock Atmel AVR microcontroller was used. A more recent innovation are optical disk drive emulators or ODDE and these often make use of FPGAs to enable them to accurately emulate timing and performance characteristics of the optical drives. Most cartridge-based console systems did not have produced for them. They usually implemented copy protection and regional lockout with game cartridges, converters or passthrough devices have been used to circumvent the restrictions, while flash memory devices were widely adopted in later years to copy game media. Modchips started to surface with the PlayStation system, due to the availability and affordability of CD writers. At the time, a sole purpose was to allow the use of imported and copied game media. Today, modchips are available for every current console system. In an effort to dissuade modchip creation, some console manufacturers included the option to run software or even an alternative operating system on their consoles. However, some of features have been withdrawn at a later date. An argument can be made that a system remains largely untouched by modchips as long as their manufacturers provide an official way of running unlicensed third-party software
9.
DVD player
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A DVD player is a device that plays discs produced under both the DVD-Video and DVD-Audio technical standards, two different and incompatible standards. Some DVD players will also play audio CDs, DVD players are connected to a television to watch the DVD content, which could be a movie, a recorded TV show, or other content. The first DVD player was created by Sony Company in Taiwan in collaboration with Pacific Digital Company from the United States in 1994, some manufacturers originally announced that DVD players would be available as early as the middle of 1996. Delivery was initially held up for reasons of copy protection demanded by movie studios. The first players appeared in Japan in November 1,1996, players slowly trickled into other regions around the world. Prices for the first players in 1997 were $1000 and up, by the end of 2000, players were available for under $100 at discount retailers. In 2003 players became available for under $50, six years after the initial launch, close to one thousand models of DVD players were available from over a hundred consumer electronics manufacturers. Fujitsu released the first DVD-ROM-equipped computer on Nov.6 in GB, Toshiba released a DVD-ROM-equipped computer and a DVD-ROM drive in Japan in early 1997. DVD-ROM drives from Toshiba, Pioneer, Panasonic, Hitachi, and Sony began appearing in sample quantities as early as January 1997, the first PC upgrade kits became available from Creative Labs, Hi-Val, and Diamond Multimedia in April and May 1997. In 2014, every major PC manufacturer has models that include DVD-ROM drives, the first DVD-Audio players were released in Japan by Pioneer in late 1999, but they did not play copy-protected discs. Matsushita first released full-fledged players in July 2000 for $700 to $1,200, DVD-Audio players are now also made by Aiwa, Denon, JVC, Kenwood, Madrigal, Marantz, Nakamichi, Onkyo, Toshiba, Yamaha, and others. Sony released the first SACD players in May 1999 for $5,000, pioneers first DVD-Audio players released in late 1999 also played SACD. SACD players are now made by Accuphase, Aiwa, Denon, Kenwood, Marantz, Philips, Sharp. A DVD player has to complete tasks, Read a DVD disc in ISO – UDF version 1. DVD players cannot play Blu-ray discs, however, most Blu-ray players are backwards compatible and they will play DVDs. Additionally, most DVD players allow users to play audio CDs, a few include a home cinema decoder. Some newer devices also play videos in the MPEG-4 ASP video compression format popular in the Internet, most hardware DVD players have to be connected to a television, there are portable devices which have an attached LCD screen and stereo speakers. Portable DVD players are used for long road trips and travel
10.
Coaxial
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In geometry, coaxial means that two or more three-dimensional linear forms share a common axis. Thus, it is concentric in three-dimensional, linear forms, a coaxial cable, as a common example, is a three-dimensional linear structure. It has a conductor in the centre, a circumferential outer conductor. The outer conductor is usually sheathed in a protective PVC outer jacket, all these have a common axis. The dimension and material of the conductors and insulation determine the characteristic impedance. In loudspeaker design, coaxial speakers are a system in which the individual driver units radiate sound from the same point or axis
11.
Ohm
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The ohm is the SI derived unit of electrical resistance, named after German physicist Georg Simon Ohm. The definition of the ohm was revised several times, today the definition of the ohm is expressed from the quantum Hall effect. In many cases the resistance of a conductor in ohms is approximately constant within a range of voltages, temperatures. In alternating current circuits, electrical impedance is also measured in ohms, the siemens is the SI derived unit of electric conductance and admittance, also known as the mho, it is the reciprocal of resistance in ohms. The power dissipated by a resistor may be calculated from its resistance, non-linear resistors have a value that may vary depending on the applied voltage. The rapid rise of electrotechnology in the last half of the 19th century created a demand for a rational, coherent, consistent, telegraphers and other early users of electricity in the 19th century needed a practical standard unit of measurement for resistance. Two different methods of establishing a system of units can be chosen. Various artifacts, such as a length of wire or a standard cell, could be specified as producing defined quantities for resistance, voltage. This latter method ensures coherence with the units of energy, defining a unit for resistance that is coherent with units of energy and time in effect also requires defining units for potential and current. Some early definitions of a unit of resistance, for example, the absolute-units system related magnetic and electrostatic quantities to metric base units of mass, time, and length. These units had the advantage of simplifying the equations used in the solution of electromagnetic problems. However, the CGS units turned out to have impractical sizes for practical measurements, various artifact standards were proposed as the definition of the unit of resistance. In 1860 Werner Siemens published a suggestion for a reproducible resistance standard in Poggendorffs Annalen der Physik und Chemie and he proposed a column of pure mercury, of one square millimetre cross section, one metre long, Siemens mercury unit. However, this unit was not coherent with other units, one proposal was to devise a unit based on a mercury column that would be coherent – in effect, adjusting the length to make the resistance one ohm. Not all users of units had the resources to carry out experiments to the required precision. The BAAS in 1861 appointed a committee including Maxwell and Thomson to report upon Standards of Electrical Resistance, in the third report of the committee,1864, the resistance unit is referred to as B. A. unit, or Ohmad. By 1867 the unit is referred to as simply Ohm, the B. A. ohm was intended to be 109 CGS units but owing to an error in calculations the definition was 1. 3% too small. The error was significant for preparation of working standards, on September 21,1881 the Congrès internationale délectriciens defined a practical unit of Ohm for the resistance, based on CGS units, using a mercury column at zero deg
12.
Volt
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The volt is the derived unit for electric potential, electric potential difference, and electromotive force. One volt is defined as the difference in potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points. It is also equal to the difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the difference between two points that will impart one joule of energy per coulomb of charge that passes through it. It can also be expressed as amperes times ohms, watts per ampere, or joules per coulomb, for the Josephson constant, KJ = 2e/h, the conventional value KJ-90 is used, K J-90 =0.4835979 GHz μ V. This standard is typically realized using an array of several thousand or tens of thousands of junctions. Empirically, several experiments have shown that the method is independent of device design, material, measurement setup, etc. in the water-flow analogy sometimes used to explain electric circuits by comparing them with water-filled pipes, voltage is likened to difference in water pressure. Current is proportional to the diameter of the pipe or the amount of water flowing at that pressure. A resistor would be a reduced diameter somewhere in the piping, the relationship between voltage and current is defined by Ohms Law. Ohms Law is analogous to the Hagen–Poiseuille equation, as both are linear models relating flux and potential in their respective systems, the voltage produced by each electrochemical cell in a battery is determined by the chemistry of that cell. Cells can be combined in series for multiples of that voltage, mechanical generators can usually be constructed to any voltage in a range of feasibility. High-voltage electric power lines,110 kV and up Lightning, Varies greatly. Volta had determined that the most effective pair of metals to produce electricity was zinc. In 1861, Latimer Clark and Sir Charles Bright coined the name volt for the unit of resistance, by 1873, the British Association for the Advancement of Science had defined the volt, ohm, and farad. In 1881, the International Electrical Congress, now the International Electrotechnical Commission and they made the volt equal to 108 cgs units of voltage, the cgs system at the time being the customary system of units in science. At that time, the volt was defined as the difference across a conductor when a current of one ampere dissipates one watt of power. The international volt was defined in 1893 as 1/1.434 of the emf of a Clark cell and this definition was abandoned in 1908 in favor of a definition based on the international ohm and international ampere until the entire set of reproducible units was abandoned in 1948. Prior to the development of the Josephson junction voltage standard, the volt was maintained in laboratories using specially constructed batteries called standard cells
13.
Attenuation
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In physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, in electrical engineering and telecommunications, attenuation affects the propagation of waves and signals in electrical circuits, in optical fibers, and in air. Electrical attenuators and optical attenuators are commonly manufactured components in this field, in many cases, attenuation is an exponential function of the path length through the medium. In chemical spectroscopy, this is known as the Beer–Lambert law, in engineering, attenuation is usually measured in units of decibels per unit length of medium and is represented by the attenuation coefficient of the medium in question. Attenuation also occurs in earthquakes, when the waves move farther away from the epicenter. One area of research in which figures strongly is in ultrasound physics. Attenuation in ultrasound is the reduction in amplitude of the beam as a function of distance through the imaging medium. Accounting for attenuation effects in ultrasound is important because a reduced signal amplitude can affect the quality of the image produced. By knowing the attenuation that an ultrasound beam experiences traveling through a medium, ultrasound attenuation measurement in heterogeneous systems, like emulsions or colloids, yields information on particle size distribution. There is an ISO standard on this technique, ultrasound attenuation can be used for extensional rheology measurement. There are acoustic rheometers that employ Stokes law for measuring extensional viscosity, wave equations which take acoustic attenuation into account can be written on a fractional derivative form, see the article on acoustic attenuation or e. g. the survey paper. Attenuation coefficients are used to different media according to how strongly the transmitted ultrasound amplitude decreases as a function of frequency. Attenuation coefficients vary widely for different media, in biomedical ultrasound imaging however, biological materials and water are the most commonly used media. Ultrasound propagation through homogeneous media is associated only with absorption and can be characterized with absorption coefficient only, propagation through heterogeneous media requires taking into account scattering. When the sun’s radiation reaches the sea-surface, the radiation is attenuated by the water. The intensity of light at depth can be calculated using the Beer-Lambert Law, in clear open waters, visible light is absorbed at the longest wavelengths first. Thus, red, orange, and yellow wavelengths are absorbed at higher water depths, because the blue and violet wavelengths are absorbed last compared to the other wavelengths, open ocean waters appear deep-blue to the eye. In near-shore waters, sea water contains more phytoplankton than the very clear central ocean waters, chlorophyll-a pigments in the phytoplankton absorb light, and the plants themselves scatter light, making coastal waters less clear than open waters
14.
Component video
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Component video is a video signal that has been split into two or more component channels. In popular use, it refers to a type of component analog video information that is transmitted or stored as three separate signals. Component video can be contrasted with composite video in all the video information is combined into a single line level signal that is used in analog television. Like composite, component-video cables do not carry audio and are paired with audio cables. When used without any qualifications the term component video usually refers to analog YPBPR component video with sync on luma. Reproducing a video signal on a device is a straightforward process complicated by the multitude of signal sources. DVD, VHS, computers and video game consoles all store, process and transmit video signals using different methods, one way of maintaining signal clarity is by separating the components of a video signal so that they do not interfere with each other. A signal separated in this way is called component video, S-Video, RGB and YPBPR signals comprise two or more separate signals, and thus are all component-video signals. In the past, for most consumer-level applications, analog component video was used, however, component video is capable of carrying various signals, such as 480i, 480p, 576i, 576p, 720p, 1080i, 1080p, 2160p and beyond. Many new high definition TVs support the use of component video up to their native resolution, most modern computers offer this signal via a VGA port. Many televisions, especially in Europe, utilize RGB via the SCART connector, all arcade games, other than early vector and black-and-white games, use RGB monitors. In addition to the red, green and blue color signals, sync on luma, where the Y signal from S-Video is used alongside the RGB signal only for the purposes of sync. Composite sync is common in the European SCART connection scheme, RGBS requires four wires – red, green, blue and sync. If separate cables are used, the cable is usually colored yellow or white. Separate sync is most common with VGA, used worldwide for analog computer monitors and this is sometimes known as RGBHV, as the horizontal and vertical synchronization pulses are sent in separate channels. If separate cables are used, the lines are usually yellow and white, yellow and black, or gray. Sync on Green is less common, and while some VGA monitors support it, sony is a big proponent of SoG, and most of their monitors use it. Like devices that use video or S-video, SoG devices require additional circuitry to remove the sync signal from the green line
15.
Non-return-to-zero
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The pulses in NRZ have more energy than a return-to-zero code, which also has an additional rest state beside the conditions for ones and zeros. For a given data signaling rate, i. e. bit rate, when used to represent data in an asynchronous communication scheme, the absence of a neutral state requires other mechanisms for bit synchronization when a separate clock signal is not available. One is represented by a DC bias on the transmission line, for this reason it is also known as on-off keying. Among the disadvantages of unipolar NRZ is that it allows for long series without change, one solution is to not send bytes without transitions. More critically, and unique to unipolar NRZ, are related to the presence of a transmitted DC level - the power spectrum of the transmitted signal does not approach zero at zero frequency. One is represented by one level, while zero is represented by another level. In clock language, in bipolar NRZ-Level the voltage swings from positive to negative on the edge of the previous bit clock cycle. An example of this is RS-232, where one is −12 V to −5 V, one is represented by no change in physical level, while zero is represented by a change in physical level. In clock language, the transitions on the trailing clock edge of the previous bit to represent a zero. This change-on-zero is used by High-Level Data Link Control and USB and they both avoid long periods of no transitions by using zero-bit insertion. HDLC transmitters insert a 0 bit after five contiguous 1 bits, USB transmitters insert a 0 bit after six consecutive 1 bits. The receiver at the far end uses every transition — both from 0 bits in the data and these extra non-data 0 bits — to maintain clock synchronization, the receiver otherwise ignores these non-data 0 bits. Non return to zero, inverted is a method of mapping a binary signal to a signal for transmission over some transmission media. The two level NRZI signal has a transition at a clock if the bit being transmitted is a logical 1. One is represented by a transition of the level, while zero has no transition. Also, NRZI might take the convention, as in Universal Serial Bus signalling, when in Mode 1, in which a transition occurs when signaling zero. The transition occurs on the edge of the clock for the given bit. However, even NRZI can have long series of zeros, magnetic disk and tape storage devices generally use fixed-rate RLL codes, while USB uses bit stuffing, which inserts an additional 0 bit after 6 consecutive 1 bits, thus forcing a transition
16.
Scrambler
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Whereas encryption usually refers to operations carried out in the digital domain, scrambling usually refers to operations carried out in the analog domain. Examples of the latter might include removing or changing vertical or horizontal sync pulses in television signals, some modern scramblers are actually encryption devices, the name remaining due to the similarities in use, as opposed to internal operation. In telecommunications and recording, a scrambler is a device that manipulates a data stream before transmitting, the manipulations are reversed by a descrambler at the receiving side. Scrambling is widely used in satellite, radio communications and PSTN modems. A scrambler can be placed just before a FEC coder, or it can be placed after the FEC, just before the modulation or line code. A scrambler in this context has nothing to do with encrypting, as the intent is not to render the message unintelligible, a scrambler replaces sequences into other sequences without removing undesirable sequences, and as a result it changes the probability of occurrence of vexatious sequences. Clearly it is not foolproof as there are sequences that yield all-zeros, all-ones. A scrambler is therefore not a substitute for a line code. An analog or digital source of unpredictable, unbiased, and usually independent output bits, a truly random generator may be used to feed a deterministic pseudo-random random number generator, which extends the random seed value. There are two reasons why scrambling is used, To enable accurate timing recovery on receiver equipment without resorting to redundant line coding. It facilitates the work of a timing circuit, an automatic gain control. For energy dispersal on the carrier, reducing inter-carrier signal interference and it eliminates the dependence of a signals power spectrum upon the actual transmitted data, making it more dispersed to meet maximum power spectral density requirements. Scramblers are essential components of physical layer system standards besides interleaved coding and they are usually defined based on linear feedback shift registers due to their good statistical properties and ease of implementation in hardware. It is common for physical layer standards bodies to refer to lower-layer encryption as scrambling as well and this may well be because mechanisms employed are based on feedback shift registers as well. Some standards for television, such as DVB-CA and MPE. Additive scramblers Multiplicative scramblers Additive scramblers transform the data stream by applying a pseudo-random binary sequence. Sometimes a pre-calculated PRBS stored in the memory is used. In order to assure a synchronous operation of the transmitting and receiving LFSR, a sync-word is a pattern that is placed in the data stream through equal intervals
17.
Synchronization
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Synchronization is the coordination of events to operate a system in unison. The familiar conductor of an orchestra serves to keep the orchestra in time, systems operating with all their parts in synchrony are said to be synchronous or in sync, those which are not are asynchronous. Today, synchronization can occur on a basis through the GPS-enabled timekeeping systems. The invention of a marine chronometer revolutionized marine navigation. By the end of the 19th century, time signals in the form of a gun, flag. Each line handled the problem by synchronizing all its stations to headquarters as a standard railroad time, in some territories, sharing of single railroad tracks was controlled by the timetable. The need for strict timekeeping led the companies to settle on one standard, in electrical engineering terms, for digital logic and data transfer, a synchronous circuit requires a clock signal. In a different sense, electronic systems are synchronized to make events at points far apart appear simultaneous or near-simultaneous from a certain perspective. Poincare phase oscillators are model systems that can interact and partially synchronize within random or regular networks, in the case of global synchronization of phase oscillators, an abrupt transition from unsynchronized to full synchronization takes place when the coupling strength exceeds a critical threshold. This is known as the Kuramoto model phase transition, synchronization is an emergent property that occurs in a broad range of dynamical systems, including neural signaling, the beating of the heart and the synchronization of fire-fly light waves. Synchronization of movement is defined as similar movements between two or more people which are temporally aligned and this is different to mimicry, as these movements occur after a short delay. Muscular bonding is the idea that moving in time evokes particular emotions and this sparked some of the first research into movement synchronization and its effects on human emotion. In dyads, groups of two people, synchronization has been demonstrated to increase affiliation, self-esteem, compassion and altruistic behaviour and increase rapport. During arguments, synchrony between the pair has been noted to decrease, however it is not clear whether this is due to the change in emotion or other factors. This is known as interpersonal synchrony, there has been dispute regarding the true effect of synchrony in these studies. Research in this area detailing the effects of synchrony, have attributed this to synchrony alone, however. Indeed, the Reinforcement of Cooperation Model suggests that perception of synchrony leads to reinforcement that cooperation is occurring, more research is required to separate the effect of intentionality from the beneficial effect of synchrony. Film synchronization of image and sound in sound film, synchronization is important in fields such as digital telephony, video and digital audio where streams of sampled data are manipulated
18.
Widescreen
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Widescreen images are a variety of aspect ratios used in film, television and computer screens. In film, a film is any film image with a width-to-height aspect ratio greater than the standard 1.37,1 Academy aspect ratio provided by 35mm film. For television, the screen ratio for broadcasts was 4,3. Between the 1990s and early 2000s,16,9 TV displays came into wide use and they are typically used in conjunction with high-definition television receivers, or Standard-Definition DVD players and other digital television sources. With computer displays, aspect ratios wider than 4,3 are also called widescreen, widescreen computer displays were previously of 16,10 aspect ratio, but now are usually 16,9. Widescreen was first used in the film of the Corbett-Fitzsimmons Fight in 1897 and this was not only the longest film that had been released to date at 100 minutes, it was also the first widescreen film being shot on 63mm Eastman stock with five perforations per frame. Widescreen was first widely used in the late 1920s in some films and newsreels. Claude Autant-Lara released a film Pour construire un feu in the early Henri Chretien widescreen process, in 1927, The American aka The Flag Maker was released. In 1926, Spoor and Berggren had released a Natural Vision film of Niagara Falls, the Natural Vision widescreen process used 63. 5mm film and had a 2,1 aspect ratio. On May 26,1929, Fox Film Corporation released Fox Grandeur News, which premiered at Graumans Chinese Theatre in Hollywood on October 2,1930, all of which were also made in the 70mm Fox Grandeur process. On November 13,1930, United Artists released The Bat Whispers directed by Roland West in a 70mm widescreen process known as Magnafilm, warner Brothers released Song of the Flame and Kismet in a widescreen process they called Vitascope. In 1930, after experimenting with the system called Fanthom Screen for The Trail of 98, MGM filmed The Great Meadow in Realife—however, its unclear if it was ever released in that widescreen process due to declining interest of the movie-going public. S. However, a few producers and directors, among them Alfred Hitchcock, have been reluctant to use the anamorphic widescreen size featured in such formats as Cinemascope. Hitchcock alternatively used VistaVision, a widescreen process developed by Paramount Pictures. Masked widescreen was introduced in April 1953, a detriment is that the film grain size is thus increased because only part of the image is being expanded to full height. Films are designed to be shown in cinemas in masked widescreen format, in such an instance, a photographer will compose for widescreen, but protect the full image from things such as microphones and other filming equipment. Standardized flat wide screen ratios are 1.66,1,1.75,1,1.85,1,1.85,1 has become the predominant aspect ratio for the format. 35mm anamorphic – This type of widescreen is used for CinemaScope, Panavision, the film is essentially shot squeezed, so that the actors appear vertically elongated on the actual film
19.
NTSC
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The first NTSC standard was developed in 1941 and had no provision for color. In 1953 a second NTSC standard was adopted, which allowed for television broadcasting which was compatible with the existing stock of black-and-white receivers. NTSC was the first widely adopted broadcast color system and remained dominant until 1997, North America, parts of Central America, and South Korea are adopting or have adopted the ATSC standards, while other countries are adopting or have adopted other standards instead of ATSC. After nearly 70 years, the majority of over-the-air NTSC transmissions in the United States ceased on January 1,2010, the majority of NTSC transmissions ended in Japan on July 24,2011, with the Japanese prefectures of Iwate, Miyagi, and Fukushima ending the next year. In March 1941, the committee issued a standard for black-and-white television that built upon a 1936 recommendation made by the Radio Manufacturers Association. Technical advancements of the side band technique allowed for the opportunity to increase the image resolution. The NTSC selected 525 scan lines as a compromise between RCAs 441-scan line standard and Philcos and DuMonts desire to increase the number of lines to between 605 and 800. The standard recommended a frame rate of 30 frames per second, other standards in the final recommendation were an aspect ratio of 4,3, and frequency modulation for the sound signal. In January 1950, the committee was reconstituted to standardize color television, in December 1953, it unanimously approved what is now called the NTSC color television standard. The compatible color standard retained full backward compatibility with existing black-and-white television sets, Color information was added to the black-and-white image by introducing a color subcarrier of precisely 315/88 MHz. These changes amounted to 0.1 percent and were tolerated by existing television receivers. The FCC had briefly approved a different color standard, starting in October 1950. However, this standard was incompatible with black-and-white broadcasts and it used a rotating color wheel, reduced the number of scan lines from 525 to 405, and increased the field rate from 60 to 144, but had an effective frame rate of only 24 frames per second. CBS rescinded its system in March 1953, and the FCC replaced it on December 17,1953, with the NTSC color standard, later that year, the improved TK-41 became the standard camera used throughout much of the 1960s. The NTSC standard has been adopted by countries, including most of the Americas. With the advent of television, analog broadcasts are being phased out. Most US NTSC broadcasters were required by the FCC to shut down their analog transmitters in 2009, low-power stations, Class A stations and translators were required to shut down by 2015. NTSC color encoding is used with the System M television signal, each frame is composed of two fields, each consisting of 262.5 scan lines, for a total of 525 scan lines
20.
PAL
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Phase Alternating Line is a colour encoding system for analogue television used in broadcast television systems in most countries broadcasting at 625-line /50 field per second. Other common colour encoding systems are NTSC and SECAM, all the countries using PAL are currently in process of conversion or have already converted standards to DVB, ISDB or DTMB. This page primarily discusses the PAL colour encoding system, the articles on broadcast television systems and analogue television further describe frame rates, image resolution and audio modulation. To overcome NTSCs shortcomings, alternative standards were devised, resulting in the development of the PAL, the goal was to provide a colour TV standard for the European picture frequency of 50 fields per second, and finding a way to eliminate the problems with NTSC. PAL was developed by Walter Bruch at Telefunken in Hannover, Germany, with important input from Dr. Kruse, the format was patented by Telefunken in 1962, citing Bruch as inventor, and unveiled to members of the European Broadcasting Union on 3 January 1963. When asked, why the system was named PAL and not Bruch the inventor answered that a Bruch system would not have sold very well. The first broadcasts began in the United Kingdom in June 1967, the one BBC channel initially using the broadcast standard was BBC2, which had been the first UK TV service to introduce 625-lines in 1964. Telefunken PALcolor 708T was the first PAL commercial TV set and it was followed by Loewe-Farbfernseher S920 & F900. Telefunken was later bought by the French electronics manufacturer Thomson, Thomson also bought the Compagnie Générale de Télévision where Henri de France developed SECAM, the first European Standard for colour television. The term PAL was often used informally and somewhat imprecisely to refer to the 625-line/50 Hz television system in general, accordingly, DVDs were labelled as PAL or NTSC even though technically the discs do not carry either PAL or NTSC composite signal. CCIR 625/50 and EIA 525/60 are the names for these standards, PAL. Both the PAL and the NTSC system use a quadrature amplitude modulated subcarrier carrying the chrominance information added to the video signal to form a composite video baseband signal. The frequency of this subcarrier is 4.43361875 MHz for PAL and NTSC4.43, the SECAM system, on the other hand, uses a frequency modulation scheme on its two line alternate colour subcarriers 4.25000 and 4.40625 MHz. Early PAL receivers relied on the eye to do that cancelling, however. The effect is that phase errors result in changes, which are less objectionable than the equivalent hue changes of NTSC. In any case, NTSC, PAL, and SECAM all have chrominance bandwidth reduced greatly compared to the luminance signal. The 4.43361875 MHz frequency of the carrier is a result of 283.75 colour clock cycles per line plus a 25 Hz offset to avoid interferences. Since the line frequency is 15625 Hz, the carrier frequency calculates as follows,4.43361875 MHz =283.75 ×15625 Hz +25 Hz
21.
Chroma subsampling
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It is used in many video encoding schemes — both analog and digital — and also in JPEG encoding. Digital signals are compressed to save transmission time and reduce file size. In compressed images, for example, the 4,2,2 YCbCr scheme requires two-thirds the bandwidth of RGB and this reduction results in almost no visual difference as perceived by the viewer. Because the human system is less sensitive to the position and motion of color than luminance. At normal viewing distances, there is no perceptible loss incurred by sampling the color detail at a lower rate, in video systems, this is achieved through the use of color difference components. The signal is divided into a component and two color difference components. In human vision there are three channels for detection, and for many color systems, three channels is sufficient for representing most colors. For example, red, green, blue or magenta, yellow, but there are other ways to represent the color. In many video systems, the three channels are luminance and two chroma channels, in video, the luma and chroma components are formed as a weighted sum of gamma-corrected RGB components instead of linear RGB components. As a result, luma must be distinguished from luminance, indeed, similar bleeding can occur also with gamma =1, whence the reversing of the order of operations between gamma correction and forming the weighted sum can make no difference. The chroma can influence the luma specifically at the pixels where the subsampling put no chroma, the parts are, J, horizontal sampling reference. A, number of samples in the first row of J pixels. B, number of changes of chrominance samples between first and second row of J pixels, may be omitted if alpha component is not present, and is equal to J when present. This notation is not valid for all combinations and has exceptions, the mapping examples given are only theoretical and for illustration. Also note that the diagram does not indicate any chroma filtering, to calculate required bandwidth factor relative to 4,4,4, one needs to sum all the factors and divide the result by 12. Each of the three YCbCr components have the sample rate, thus there is no chroma subsampling. This scheme is used in high-end film scanners and cinematic post production. Note that 4,4,4 may instead be referring to RGB color space, formats such as HDCAM SR can record 4,4,4 RGB over dual-link HD-SDI
22.
Rec. 601
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It includes methods of encoding 525-line 60 Hz and 625-line 50 Hz signals, both with an active region covering 720 luminance samples and 360 chrominance samples per line. The color encoding system is known as YCbCr 4,2,2, the standard has been revised several times in its history. Its edition 7, referred to as BT. 601-7, was approved in March 2011 and was published in October 2011. The Rec.601 signal can be regarded as if it is a digitally encoded analog component video signal, regardless of the frame rate, the luminance sampling frequency is 13.5 MHz. The samples are uniformly quantized using 8 or 10 bit PCM codes in the YCbCr domain, for each 8 bit luminance sample, the nominal value to represent black is 16 and the value for white is 235. Eight-bit code values from 1 through 15 provide footroom, and can be used to accommodate transient signal content such as filter undershoots, similarly, code values 236 through 254 provide headroom and can be used to accommodate transient signal content such as filter overshoots. The values 0 and 255 are used to encode the sync pulses and are forbidden within the picture area. The Cb and Cr samples are unsigned and use the value 128 to encode the neutral color difference value, as used when encoding a white, slightly different primaries are specified for the 625 line and 525 line systems. Rec.601 defines a nonlinear transfer function which is linear near 0 and then transfers to a gamma curve for the rest of the light intensity range. E = {4.500 L L <0.0181.099 L0.45 −0.099 L ≥0.018 The CCIR received a 1982–83 Technology,709, the corresponding standard for high-definition television Rec. 2020, ITU-R Recommendation for ultra-high-definition television ITU-R BT.656, ITU-R Recommendation for parallel and serial transmission formats for BT.601 video Pixel aspect ratio
23.
YCbCr
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YCbCr, Y′CbCr, or Y Pb/Cb Pr/Cr, also written as YCBCR or Y′CBCR, is a family of color spaces used as a part of the color image pipeline in video and digital photography systems. Y′ is the component and CB and CR are the blue-difference and red-difference chroma components. Y′ is distinguished from Y, which is luminance, meaning that light intensity is nonlinearly encoded based on gamma corrected RGB primaries, Y′CbCr color spaces are defined by a mathematical coordinate transformation from an associated RGB color space. If the underlying RGB color space is absolute, the Y′CbCr color space is a color space as well, conversely, if the RGB space is ill-defined. By doing this, subsequent image/video processing, transmission and storage can do operations, one practical example would be decreasing the bandwidth or resolution allocated to color compared to black and white, since humans are more sensitive to the black-and-white information. YCbCr is sometimes abbreviated to YCC, Y′CbCr is often called YPbPr when used for analog component video, although the term Y′CbCr is commonly used for both systems, with or without the prime. Here, the prime ′ symbols mean gamma correction is being used, thus R′, G′ and B′ nominally range from 0 to 1, with 0 representing the minimum intensity and 1 the maximum. The resulting luma value will then have a range from 0 to 1. The reverse conversion process can be derived by inverting the above equations. When representing the signals in digital form, the results are scaled and rounded, for example, the scaling and offset applied to the Y′ component per specification results in the value of 16 for black and the value of 235 for white when using an 8-bit representation. The standard has 8-bit digitized versions of CB and CR scaled to a different range of 16 to 240 and this head-room and toe-room can also be used for extension of the nominal color gamut, as specified by xvYCC. The value 235 accommodates a maximum black-to-white overshoot of 255 -235 =20, or 20 / =9. 1%, the toe-room is smaller, allowing only 16 /219 =7. 3% overshoot, which is less than the theoretical maximum overshoot of 8. 9%. This causes some difficulty in determining how to interpret and display some YCbCr signals. These out-of-range YCbCr values are used by xvYCC to encode colors outside the BT.709 gamut and this allows for the value 256 in the denominator, which can be calculated by a single bitshift. A different form of Y′CbCr is specified in the ITU-R BT.709 standard, the newer form is also used in some computer-display oriented applications. In this case, the values of Kb and Kr differ, but the formulas for using them are the same. The definitions of the R, G, and B signals also differ between BT.709 and BT.601, and differ within BT.601 depending on the type of TV system in use, and differ further in other specifications. So proper conversion of Y′CbCr from one form to the other is not just a matter of inverting one matrix, the ITU-R BT.2020 standard defines both gamma corrected Y′CbCr and a linear-encoded version of YCbCr called YcCbcCrc
24.
Luminance
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Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light passes through, is emitted or reflected from a particular area. The SI unit for luminance is candela per square metre, a non-SI term for the same unit is the nit. The CGS unit of luminance is the stilb, which is equal to one candela per square centimetre or 10 kcd/m2, luminance is often used to characterize emission or reflection from flat, diffuse surfaces. The luminance indicates how much power will be detected by an eye looking at the surface from a particular angle of view. Luminance is thus an indicator of how bright the surface will appear, in this case, the solid angle of interest is the solid angle subtended by the eyes pupil. Luminance is used in the industry to characterize the brightness of displays. A typical computer display emits between 50 and 300 cd/m2, the sun has luminance of about 1. 6×109 cd/m2 at noon. Luminance is invariant in geometric optics and this means that for an ideal optical system, the luminance at the output is the same as the input luminance. For real, passive, optical systems, the luminance is at most equal to the input. As an example, if one uses a lens to form an image that is smaller than the source object, the luminous power is concentrated into a smaller area, meaning that the illuminance is higher at the image. The light at the plane, however, fills a larger solid angle so the luminance comes out to be the same assuming there is no loss at the lens. The image can never be brighter than the source, if light travels through a lossless medium, the luminance does not change along a given light ray. In the case of a perfectly diffuse reflector, the luminance is isotropic, then the relationship is simply L v = E v R / π A variety of units have been used for luminance, besides the candela per square metre. One candela per square metre is equal to, 10−4 stilbs π apostilbs π×10−4 lamberts 0.292 foot-lamberts Retinal damage can occur when the eye is exposed to high luminance, damage can occur due to local heating of the retina. Photochemical effects can cause damage, especially at short wavelengths. Also available in PDF form and Google Docs online version Autodesk Design Academy Measuring Light Levels
25.
Chrominance
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Chrominance is the signal used in video systems to convey the color information of the picture, separately from the accompanying luma signal. Chrominance is usually represented as two color-difference components, U = B′ − Y′ and V = R′ − Y′, each of these difference components may have scale factors and offsets applied to it, as specified by the applicable video standard. In digital-video and still-image color spaces such as Y′CbCr, the luma, separating RGB color signals into luma and chrominance allows the bandwidth of each to be determined separately. Typically, the bandwidth is reduced in analog composite video by reducing the bandwidth of a modulated color subcarrier. The idea of transmitting a color signal with distinct luma and chrominance components originated with Georges Valensi. Previous schemes for color television systems, which were incompatible with existing monochrome receivers, in analog television, chrominance is encoded into a video signal using a subcarrier frequency. Depending on the standard, the chrominance subcarrier may be either quadrature-amplitude-modulated or frequency-modulated. In the PAL system, the subcarrier is 4.43 MHz above the video carrier. The NTSC and PAL standards are the most commonly used, although there are other standards that employ different subcarrier frequencies. For example, PAL-M uses a 3.58 MHz subcarrier, the presence of chrominance in a video signal is indicated by a color burst signal transmitted on the back porch, just after horizontal synchronization and before each line of video starts. If the color burst signal were visible on a television screen, in NTSC and PAL, hue is represented by a phase shift of the chrominance signal relative to the color burst, while saturation is determined by the amplitude of the subcarrier. In SECAM and signals are transmitted alternately and phase does not matter, chrominance is represented by the U-V color plane in PAL and SECAM video signals, and by the I-Q color plane in NTSC. Digital video and digital photography systems sometimes use a luma/chroma decomposition for improved compression. On decompression, the Y′CbCr space is rotated back to RGB
26.
RGB color model
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The RGB color model is an additive color model in which red, green and blue light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three primary colors, red, green and blue. Before the electronic age, the RGB color model already had a theory behind it. Thus an RGB value does not define the same color across devices without some kind of color management, typical RGB input devices are color TV and video cameras, image scanners, video games, and digital cameras. Typical RGB output devices are TV sets of technologies, computer and mobile phone displays, video projectors, multicolor LED displays. Color printers, on the hand are not RGB devices. This article discusses concepts common to all the different color spaces that use the RGB color model, to form a color with RGB, three light beams must be superimposed. Each of the three beams is called a component of color, and each of them can have an arbitrary intensity, from fully off to fully on. The RGB color model is additive in the sense that the three beams are added together, and their light spectra add, wavelength for wavelength. This is essentially opposite to the color model that applies to paints, inks, dyes. When the intensities for all the components are the same, the result is a shade of gray, darker or lighter depending on the intensity. When the intensities are different, the result is a colorized hue, a secondary color is formed by the sum of two primary colors of equal intensity, cyan is green+blue, magenta is red+blue, and yellow is red+green. The RGB color model itself does not define what is meant by red, green and blue colorimetrically, and so the results of mixing them are not specified as absolute, but relative to the primary colors. When the exact chromaticities of the red, green and blue primaries are defined, the normal three kinds of light-sensitive photoreceptor cells in the human eye respond most to yellow, green, and violet light. As an example, suppose that light in the range of wavelengths enters the eye. Light of these wavelengths would activate both the medium and long wavelength cones of the retina, but not equally—the long-wavelength cells will respond more, the difference in the response can be detected by the brain, and this difference is the basis of our perception of orange. Thus, the appearance of an object results from light from the object entering our eye and stimulating the different cones simultaneously. The first experiments with RGB in early color photography were made in 1861 by Maxwell himself, to reproduce the color photograph, three matching projections over a screen in a dark room were necessary
27.
Interlaced video
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Interlaced video is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth. The interlaced signal contains two fields of a video frame captured at two different times and this enhances motion perception to the viewer, and reduces flicker by taking advantage of the phi phenomenon. This effectively doubles the resolution as compared to non-interlaced footage. Interlaced signals require a display that is capable of showing the individual fields in a sequential order. CRT displays and ALiS plasma displays are made for displaying interlaced signals, Interlaced scan refers to one of two common methods for painting a video image on an electronic display screen by scanning or displaying each line or row of pixels. This technique uses two fields to create a frame, one field contains all odd-numbered lines in the image, the other contains all even-numbered lines. A Phase Alternating Line -based television set display, for example, the two sets of 25 fields work together to create a full frame every 1/25 of a second, but with interlacing create a new half frame every 1/50 of a second. To display interlaced video on progressive displays, playback applies deinterlacing to the video signal. The European Broadcasting Union has argued against interlaced video in production and they recommend 720p 50 fps for the current production format—and are working with the industry to introduce 1080p 50 as a future-proof production standard. 1080p 50 offers higher vertical resolution, better quality at lower bitrates, despite arguments against it, television standards organizations continue to support interlacing. It is still included in digital video formats such as DV, DVB. Progressive scan captures, transmits, and displays an image in a similar to text on a page—line by line. The interlaced scan pattern in a CRT display also completes such a scan, the first pass displays the first and all odd numbered lines, from the top left corner to the bottom right corner. The second pass displays the second and all even numbered lines and this scan of alternate lines is called interlacing. A field is an image that contains only half of the lines needed to make a complete picture, persistence of vision makes the eye perceive the two fields as a continuous image. In the days of CRT displays, the afterglow of the displays phosphor aided this effect, interlacing provides full vertical detail with the same bandwidth that would be required for a full progressive scan of twice the perceived frame rate and refresh rate. To prevent flicker, all analog broadcast television systems used interlacing, format identifiers like 576i 50 and 720p 50 specify the frame rate for progressive scan formats, but for interlaced formats they typically specify the field rate. This can lead to confusion, because industry-standard SMPTE timecode formats always deal with frame rate, not field rate
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